1. Field of the Invention
The present invention relates to a motor control apparatus provided with a magnetic flux control unit, and a machine learning apparatus and a method thereof.
2. Description of the Related Art
An induction motor is configured to cause a primary current to flow in a stator to generate a rotating magnetic field and allow a rotor to cut a magnetic flux generated by the rotating magnetic field so that voltage is induced in the rotor and a secondary current flows, and cause a torque to be generated by an interaction between the secondary current and the magnetic flux. In the related art, vector control, which is a method of controlling the primary current to be passed through the stator by dividing into an excitation current, flowing in a direction of a magnetic flux, and the secondary current, i.e., a torque current is employed as a method of controlling the induction motor. Generated torque is proportional to a product of the magnetic flux generated by the excitation current and the torque current.
Although a magnitude of the magnetic flux in the induction motor in a steady state is proportional to the excitation current generating the magnetic flux, when causing the magnetic flux to vary in association with a variation in load applied to the induction motor and operating conditions, the magnetic field varies with a primary delay with respect to the variation in excitation current.
FIG. 8 is an explanatory drawing illustrating a load applied to an induction motor that drives a drilling machine. FIG. 9A is a drawing depicting an operation mode, an excitation current, and a magnetic flux in the induction motor that drives the drilling machine in FIG. 8, and illustrating an operation mode (drilling) of the induction motor. FIG. 9B is a drawing depicting the operation mode, the excitation current, and the magnetic flux in the induction motor that drives the drilling machine in FIG. 8, and illustrating an excitation current flowing in the induction motor and a magnetic flux that is generated by the excitation current. A load applied to the induction motor (not illustrated) that drives a drilling machine 81 when the drilling machine 81 forms a hole 92 in a member 91 (a drilling operation mode) is larger than a load applied to the induction motor (not illustrated) that drives the drilling machine 81 when pulling out a drill of the drilling machine 81 from the hole 92 after the drilling has terminated or when moving the drilling machine 81 to a subsequent point of drilling (a drill movement operation mode). Therefore, when the drilling machine 81 forms the hole 92 in the member 91, the operation mode of the induction motor is switched from the drill movement operation mode to the drilling operation mode so as to cope with a high load. As illustrated in FIG. 9A, when switching the induction motor that drives the drilling machine 81 to the drilling operation mode at time t1 for the drilling with the drilling machine 81, excitation is started at time t1, for which an excitation current command for the corresponding drilling operation mode is output from the motor control apparatus (not illustrated) and, accordingly, the excitation current (illustrated by a dot-and-dash line) for the corresponding drilling operation mode as illustrated in FIG. 9B flows in the induction motor. However, since the magnetic flux (illustrated by a solid line) that is generated by the excitation current varies with a primary delay having, as a time constant, a circuit constant of the induction motor with respect to the excitation current, for example, a period “t2-t1” may be needed until the torque that may be required for the drilling reaches the maximum magnetic flux with which the drilling may need a full torque from the start of the excitation at time t1, where clock t2 is time when the maximum magnetic flux with which the drilling may need the full torque occurs.
Since the magnetic flux of the induction motor is established with a delay with respect to the excitation current in this manner, if current control is performed without considering the primary delay, the torque varies discontinuously with a variation in magnetic flux at the time of acceleration or deceleration of the induction motor, so that a transient phenomenon that a velocity waveform swells may occur. Therefore, in the control of the induction motor, quick increase and change of a magnetic flux corresponding to a variation in load and operation condition may be demanded.
For example, as described in Japanese Unexamined Patent Publication No. 2008-306798, as a method of controlling a motor for expediting the increase of the magnetic flux, there is a technology of passing an excitation current not lower than a rated current from a time point when timing to start increasing magnetic flux is reached such as switching of the operation mode.
However, according to the invention descried in Japanese Unexamined Patent Publication No. 2008-306798, since the magnetic flux is increased from a time point when timing to start increasing the magnetic flux is reached, lead time for the magnetic flux to be increased to the desired level (hereinafter, referred to as “magnetic flux increase lead time”) cannot be completely eliminated.
In addition, easy and optimum control of the magnetic flux of induction motors, which may be driven in various operating patterns, is still widely desired.